1. Field of the Invention
The invention relates to patient safety and controllers, and, more specifically, to a patient lifting apparatus and a controller that permits operation of a patient lifting mechanism within a specified safe range of operation.
2. Description of the Background
It is well known that persons confined to a bed due to illness, age, accident, or injury and so forth possess such limited mobility that movement or transfer is extremely difficult. Improper transfer can result in serious complications to the individual arid the care giver. For instance, the need to move a patient immediately after an operation may be necessary, yet is a dangerous proposition, as any movement of the body may undo a surgeon""s most careful work. Just as important is the need to transfer a bed ridden person for bathing or exercise so as to facilitate recovery.
In a hospital setting, a transfer is typically performed by a number of hospital workers, in order to comfortably lift a patient from one position to another. If the transfer is made only by hand, the hospital personnel risk back injury. If the transfer utilizes too few personnel, or requires reaching in an awkward position, the personnel may risk body strain. Further, despite the number of personnel employed to assist in the transfer, the patient is susceptible to injury from anyone who touches or lifts incorrectly.
For these reasons, a number of devices have been developed for lifting and lowering of incapacitated persons from a position in a bed, chair, bath or the like, such as a patient lift device having a base frame having vertically oriented guideposts, wherein a carriage assembly moves along the guideposts in response to an operator applied control signal. An arm assembly projects over the person placed into a sling for lifting. Such a device may require sufficient size to accomplish the intended service, namely, lifting. In particular, the device may employ elongated legs and a boom that is necessary to lift a patient. This may prevent the device from being easily transferred or stored. The length of the components are necessary so that the apparatus can fit beneath a bed or chair, yet provide sufficient support during the lifting process.
Another example of a patient lift and transfer apparatus includes a unitary frame having a caster wheel equipped U-shaped horizontal disposed frame. Again, the legs of this apparatus are capable of being placed beneath a patient""s bed providing sufficient support for the lifting device as well as the patient. However, no provision is made for storage or transportation of the apparatus.
Another apparatus is based upon electrical motors to provide assistance in patient movement, wherein the arm members telescope and then retract. This apparatus does not include the retraction of the arms for purposes of storage or transportation.
A lifting device having leg support structures in the form of telescoping leg assemblies capable of extension and divergence is stable and may provide a safe and effective means of lifting patients. An example of such a lifting device is provided in U.S. Pat. No. 6,026,523, incorporated herein by reference in its entirety. The lifting device of this patent meets the particular problems commonly found in hospitals and convalescent homes, wherein short term lifting capabilities are necessary. Unique to this lifting device is the ability to lift up to six hundred pounds, yet retract in size for purposes of transporting and storage. In operation, the support legs provide about a seventy eight inch stance when fully extended. In a retracted position, the support legs telescope together, leaving a frame footprint of approximately fifty two inches. The lifting device includes a miniature crane having a rotatable column with a lifting arm that can be raised and lowered at the upper end. The column is rotatably coupled to the portable base frame, and is operably attached to an electric motor driven linear actuator that enables independent and reversible rotation of the column, in order to facilitate placement of the end of the lifting arm above the patient""s bed, in order to permit eventual transport of the patient away from the bed, such as by, for example, a chair, gurney, or wheelchair. An additional electric motor driven linear actuator may make raising and lowering of the lifting arm effortless.
The support legs may be further extended outwardly from the frame once the apparatus is positioned at the bedside. This feature allows for ease of movement to various sites, but allows for greater stability during use. Additionally, the support legs, which are normally parallel with respect to each other, are pivotally attached to the base frame and operatively associated with an additional electrically driven linear actuator. Operation of this actuator enables angular displacement of the leg assemblies, so as to cause divergence or convergence thereof. This feature provides a safe and efficient means to ensure the stability of the entire apparatus during a lifting procedure. Additionally, since the extension and divergence of the support legs is carried out beneath the bed, access to the bed and the patient is not hampered in any way.
Once the apparatus is in position, the unit can be easily secured by locking the frame mounted wheels. In an embodiment, the apparatus uses four wheels, two of which are lockable caster wheels similar to those found on stretchers, positioned at the rear of the support base. Two additional casters are affixed to the lower portion of the support legs at their outermost or distal end.
With the support legs in an extended and divergent position, an operator can maneuver the lifting arm over a patient""s bed, wherein a hook device is available for attaching to a patient sling. The sling is placed beneath the patient so as to facilitate support during transfer. The combination of actuator and lifting arm is capable of lifting up to six hundred pounds. Through an angular range of motion of about 50-90 degrees along the vertical axis. The column is further able to rotate about its axis on the order of about +/xe2x88x9230 degrees from a starting position, e.g. perpendicular to the rear edge of the support base, in either a clockwise or counterclockwise direction. Angular rotation of the column is performed by use of an electric motor coupled to a linear actuator.
An operator of the lifting device controls operation by sending control signals to the controller that, in turn, forwards control signals to actuators to generate the movement of the lifting device in accordance with the control signal. However, the methodology used to provide the control signal from the operator, such as a hand-held control pad, having thereon a plurality of control buttons, such as extend, lift, right, left, up, down, and the like, may be, intentionally or unintentionally, misused by the operator. In such an instance, the lifting device may not operate properly or safely. For example, if a safe footprint of the lifting device is not set before attempting a lift and transfer of the patient, such as by a failure to extend the base, or a failure to sufficiently open the legs, the base may allow for tipping over of the lifting device, thereby possibly harming the patient or the operator. When the legs are completely open angularly, and when the legs are completely extended linearly, a safe footprint is set, thereby allowing for lift and transfer with no tipping.
Recommendations to the operator, such as in the form of extensive in-service training emphasizing proper setup, and/or instructions included with signage placed on the lifting device, can assist in insuring proper setup of the lifting device. However, such training or informational methodologies nonetheless allow for human error. Thus, an automated device and method is needed to completely insure proper setup of the lifting device.
A computerized controller that limits the movement of a patient lifting device, wherein the controller is operated in a normal mode to sense the lateral rotation of a lifting arm that lifts patients and the linear displacement of extendable support legs for said lifting device and the angular diversion of said support legs, is disclosed. The controller inhibits movement of said lateral rotation of a lifting arm in response to the linear displacement and the angular diversion of the support legs to prevent tipping the lifting device.
A computerized controller that limits the movement of a patient lifting device, in a normal mode of operation, whereby tipping of the lifting device is prevented, is also disclosed. The controller is operated in a bypass mode to override the normal mode wherein the patient lifting device may be operated during a setup and breakdown operation to permit construction and disassembly of the patient lifting device.